Process of making chromium iron alloys



Patented Dec. 5, 1944 I PROCESS OF MAKING GHRGMIUMI mo ALLOYS Joseph J. Vetter, Hackensack, N. 3., assignor to Natural Products Refining (30., Jersey City,

N. .l., a corporation of Delaware No Drawing. Application July 6, 1942, Serial No. {149.967

' 2 Claims.

My invention relates particularly to a process of producing chromium iron alloys having many advantageous properties.

The object of my invention is to obtain an alloy containing chromium and iron having extraor dinary hardness as well'as other valuable properties; Preferably, the alloys thus obtained have a high chromium content, a high carbon content and a high percentage of silicon. These alloys are capable of being used to great advantage in many different Ways, but they also can be admixed with other metals or alloys to impart more or less of their properties, as desired, to the final alloys which may be thus produced. A further object of my invention is to provid a process of the above character in which a silicic substance is employed in the smelting operation from which the silicon, present in the resulting alloy, may

For example, in carrying out my invention I may make a mixture containing a ground residue from a chromate extraction of chromium iron ores (usually containingabout 50% of chromium by weight), the said residue being, for example,

the'residue obtained in accordance with the process of my patent above referredto and which may produce a residue containing as low as' 2.5%

CI'zOs by weight with the percentages of recoveries there given, although other residues from chromate extraction-may be used, but the residue employed will usually contain from 4 to 8% by weight of chromium oxide, as well as oxides .of iron. aluminum, silicon, calcium and magnesium. The amount of said residue utilized will be about 65 to 80% by Weight of the mixture to be smelted.-

With this, I admix an amount of a reducing agent, such for example as coke or soft coal or any other form of carbon, equal to about 10 to 15% by I weight of the entire mixture to be smelted. In

the mixture, I also introduce as a slag-forming material, asilicic substance such for example as a silica-containing rock or a clay containing silica, or a silicic substance such as, for example,

a silicate, Or a silicate-containing rock or a clay containing a silicate, for instance fire brick clay,

' amounting tofrom 5 to 15% by weight of the entire mixture. This is about enough of the silicic material to prevent the temperature becoming so highas to melt the available refractory linings. The clay which I prefer to use for this purpose is an aluminum silicate bearing clay, or an aluminumsilicate bearing rock, and I might substitute for the coal or the slag-forming material or both in whole or in part a high carbon silicatecontain ing shale, such as low grade high-ash coal; This mixture is introduced into a furnace which may bean electrically heated furnace or an electric arc furnace, in which the mixture is heated to a temperature of 2500 to 3000 F.; but preferably 2800 F., until thoroughly liquefied, thus formin a body of molten alloy with a supernatant layer of slag. The smelting is carried out in an atmospher of the products of combustion produced.

The alloy thus obtained. will comprise from 15 to 25% by weight of chromium, from 1 to 3% by weight of silicon, and from 1 to 6% by weight of carbon, the balance being comprised substantially entirely of iron. The alloy containing even this high chromium content has great toughness, probably due to the absence of any uncombined graphitic carbon. The amount of carbon present within the range referred to may be varied and isgreater according to the increase of the amount of the above carbonaceous reducing agent put in the charge and the increase of the length of time the charge is in the furnace. When the carbon is 2% or higher, probably all of the chromium is in the form of achromium carbide, which is extraordinarily hard, but when the carbon is below 2% some of the chromium appears to be not in the form of a carbide so that the properties of the alloy are materially changed accordingly. The alloys thus obtained, because of their very great hardness and length of wear, have many useful applications, as for example in spiral screw conveyors for conveying gritty materials, bearings, shafts, etc. When the alloy obtained contains from 5 to 6% by weight of carbon the alloy is of extraordinary hardness and is very dilficult to grind except with a diamond wheel. The alloy, having a'ran'ge of carbon from 1 to 6%, when cast in molds of any desired character, as for exam- 'ple in cast iron, graphite or sand molds, furthermore, has the properties of forged steel, including the very fine grain, without having to be put through the expensive forging and heat-treating operations necessary in producing forged steel.

Also, the surface of the alloy when polished is so smooth as to seem to have been lubricated. At high temperatures the alloy also has remarkable properties, inasmuch as when heated up to 1500 F. or higher it has a very unusual amount of rigidity. This is demonstrated by the testing of A a bar thereof supported at its ends and subjected o weights applied thereto between the supports.

Under these conditions little or no sagging takes place, whereas ordinary steel without any weights being applied will readily sag of its own weight at such temperatures. When the carbon content is less than 5%. but at least as high as 1%, the alloy is more ductile than when the carbon is above 5% but it is still too hard to saw and too hard to be forged. When, however, the carbon content is lowered below 1% the alloy can be sawed, drilled, etc. The alloys containing a content of 1% to 5% by weight of carbon are, therefore, useful in producin gears when great toughness is needed and brittleness is to be avoided.

When alloys are desired of a considerably increased toughness, as for example in making tools, hammers, chisels and cutters, I may dilute the alloy by adding from up to 100% by weight of the alloy to a mild steel (for example a steel containing about 5% by weight of carbon) in an amount to make up the balance of the 100%. One example of this would be an alloy obtained by incorporating by weight of any of my alloys described initially above, containing 1 to reducing agent for use with the iron ore.

6% by weight of carbon, with 80% by weight oi.

the mild steel. Another example. would be by incorporating 10% by weight of any of my said alloys containing from 1 to 6% by weight of carbon with 90% by weight of the mild steel. These diluted alloys can be obtained instead, however,

byadding in the original charge used in the first n entioned smelting operation herein, an equivalent amount of iron or mild steel or even an equivalent amount of iron ore and carbonaceous example, hammers made with this diluted alloy have been found, by testing, to have a superior hardness and toughness than the best forged steel hammers previously available.

It is to be understood also that a small amount, up to a total of /2%, in any one of the above alloys, may be comprised of any one or more of the following:

Molybdenum Tungsten t Manganese which may be present therein as impurities, although it is preferred not to have any of them present.

While I have described my invention above in detail I wish it to be understood that many changes may be made therein without departing from the spirit of the same.

' I claim:

1. A process which comprises producing a chromium iron alloy containing at least iron by weight by smelting together a residue, containing a minimum of approximately 2.5% CI2O by weight, obtained from the extraction of a chromate from chromium iron ore, with a high carbon silicate containing shale.

' 2. A process which comprises producing a chromium iron alloy containing at least 65% iron by weight by smelting together a residue, containing a'minimum of approxiately 2.5% one; by weight, obtained from the extraction of a chromate from chromium iron ore, with a low grade high-ash coal.

JOSEPH J. VE'ITER.

For 

